Change is in the air for next season all Nascar engines will run an electronic fuel-injection system supplied by McLaren Racing. Nascar found that this formula ensured close-fought competition between a variety of manufacturers and teams, and they have stuck with it even as street cars began to use advanced technology like variable-cam timing and fuel injection. Some vestiges of the old days remain: For instance, Nascar engines must use a carburetor, pushrods, two valves per cylinder and a wedge-shaped combustion chamber-that's right, no hemis allowed. Stock car racing began with slightly modified versions of street-car engines, but over the years the stock car engine has become less and less 'stock' as it has used fewer and fewer production car parts.

But today, the engine under Jimmie Johnson's hood is a custom-made 850-hp 358-cubic-inch thoroughbred that's optimized to run flat-out for no more than 1000 miles. The engines in Nascar Sprint Cup cars are 90-degree pushrod V8s, just like those that have powered many vehicles on American roads for more than 50 years.

What is a stock car